In a conventional heating system, an enclosed region is heated by hot water circulated through a heat exchanger in the region. The water is heated in a boiler which in turn receives heat from a furnace in which oil, gas or other fuel is burned. A circulator pump circulates water from the boiler to the exchanger and back to the boiler. During the heating season, the water in the boiler is maintained between a minimum preselected temperature such as 100.degree. F. and a maximum preselected temperature such as 190.degree. F. When the region is heated, the requisite heat is supplied via the heat exchanger from the circulating hot water which is cooled accordingly. This cooled water is circulated back into the boiler for reheating prior to subsequent reuse. Thus additional heat is supplied via the boiler which in turn must continue to receive heat from the furnace. A thermostat in the region is used to turn both the circulator pump and furnace on at the same time when calling for heat and to turn the pump and furnace off at the same time when there is sufficient heat in the region and the thermostat is satisfied.
Since the water in the boiler has been maintained at a temperature during the heating circle which is well above the minimum temperature it will have cooled down slowly to the minimum temperature after the heating cycle is completed. During such cooling operation heat is lost and effectively wasted. This is a significant waste because the cost of the energy (fuel) used to produce the waster heat is significant and at the present time continually increasing.
The present invention is directed toward apparatus for controlling the operation of a heating system wherein the wasted heat previously described can be used to supply additional heat to the region. Thus, the previously wasted heat is converted to useful heat. This enables the system to deliver the same total heat to the region while substantially reducing the energy requirements and cost of operation.